Low voltage starting circuit



R. F..| |AY$, JR Lovi .VOLTAGE lSTARTING CIRCUIT Filed oei. 1.V 1940 l ll l ammi-aumm2' ,I L 1-- l' "wl-:arrowl z. A? Ara, .nr- Y MMS/m.ATTORNEY dwz/Mur ttxivz Patented Dec. 1li, 1942 21,305,474 Low VOLTAGE.STARTING cmoUrr Robert F. Hays, Westinghouse Jr., Bloomfield, N. J.,assignor to Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application October 1, 1940, Serial 5Claims. I(Cl. 176-124) The present invention relates to gaseousdischarge devices and more particularly to apparatus for starting andoperating such devices, especially what are now Well known to the art asfluorescent lamps.

In order to adapt fluorescent lamps tol commercial and domestic use, itis essential that they be operable from the customary domestic source ofsupply of 115-230 volts. Inasmuch as a higher voltage is required toinitiate a discharge than to sustain the same, auxiliary startingequipment is necessary in order that a starting voltage higher thannormal line voltage is available.

Where such fluorescent lamps are of relatively low wattage ranging fromapproximately 15 to 40 watts and where connected to a lagging powerfactor circuit, the auxiliary starting equipment is now of exceedinglysimple and compact construction. Such equipment usually consists ofmerely an inductance element in series with one of the electrodes of thelamp and a starting relay, as shown in Patent 2,200,443, yissued May 14,1940, to E. C.A Dench, and assigned to the same assignee as the presentinvention, which operates to initially connect the electrodes in aseries heating circuit.

However, as the wattage per unit length of such fluorescent lampsincreases, the ratio of peak lamp voltage to average lamp voltagebecomes greater, with the result that it is not feasible to 3 employ aglow relay tube, such as shown in the above mentioned patent, inconnection with a leading power factor circuit under certain conditions,although no difficulties are encountered with lagging power factorcircuits.

A lagging power factor circuit, however, particularly in large domesticand. commercial installations, naturally decreases the efficiency of theentire installation, which can be corrected to a material extent by theutilization of a leading power factor circuit. In such installations,however, it has not been heretofore practical as above noted to employ astarting relay of the above noted type when operating the lamp from a115 volt line because the peak lamp voltage exceeds peak line voltage,with the result that such relay would ordinarily continue to functioneven after the lamp has started. Such condition even with a leadingpower factor circuit, however, does not exist where between line voltageand lamp voltage.

It is accordingly an object of the present invention to provide astarting and operating arthere is a sufficiently wide range lamp inaccordance with rangement for gaseous discharge lamps which is ofcompact nature and which operates with high eiilciency and goodstability yet is exceeding economical to manufacture.

Another object of the Apresent invention is the provision of a startingand operating circuit for gaseous discharge lamps of comparatively highwattage wherein the auxiliary starting equipment includes a glow relaytube which operates at a voltage suciently above lamp Voltage that thelamp is readily started without repetitous operation of the relay duringoperation of the lamp.

Another object of the present invention is the provision of astartingand operating circuit for gaseous discharge lamps which can bereadily started by the employment of a glow relay tube from a supplysource having a voltage but slightly higher than lamp voltage.

Another object of the present invention is the provision of a leadingpower factor circuit for starting and operating gaseous discharge lampswherein the cost, weight and size of the auxiliary equipment ismaterially reduced by the utilization of a glow relay tube.

A further object of the present invention is the provision of a startingand operating circuit for gaseous discharge lamps wherein thestroboscopic elect of a two-lamp unit is materially re-l duced.

Still further objects of the present invention will become obvious tothose skilled in the art by reference to the accompanying drawingwherein:

Fig. l is a diagrammatic illustration of a starting and operatingcircuit for a gaseous discharge the present invention.

Fig. 2 is a graphic lillustration of the wave form of the current,magnetic flux, and voltage in the saturable reactor which forms a partof the leading power factor circuit for starting and operating a lamp inaccordance with the present invention.

Fig. 3 is a diagrammatic illustration of'a starting and operatingcircuit for a two-lamp unit constructed in accordance with the presentinvention wherein one of the lamps has a leading power factor and theother a lagging power factor.

Referring now to the drawing in Adetail for a better understanding ofthe present invention, a gaseous discharge lamp 5 of the fluorescenttype is shown in Fig. 1 which is provided with a pair of electrodes 6and 1. As will be noted, one terminal of the electrode 6 is connected bya conductor 8, capacitor 9 and inductance element I0,

trode 'l is connected by a conductor I2 to the other side of the sourceof supply while the remaining terminals of the electrodes 6 and .'l areconnected together by a glow relay tube I3 of the type shown anddescribed in the above noted Patent 2,200,443. This arrangement thusmakes a leading power factor circuit for energizing the lamp which tendsto increase the eiciency of a given installation of several lamps andenables the utilization of a glow relay, such as shown at I3. Asaturable reactor I4, which may consist of approximately 1200 turns ofne wire wound on a x interleaved core, is connected in electricalparallel with the lamp 5 and such reactor together with capacitor 9 andinductance element I may be enclosed in a housing or casing I5, as shownin dotted lines in Figs. 1 and 3.

To start the lamp a switch (not shown) is first closed which connectsthe unit to the source of supply of approximately 118 volts. Uponclosure of such switch, a voltage is impressed across the reactor I4,through a circuit including the capacitor 9 and inductance element I0,which voltage is equal to line voltage plus the voltage drop in theseries connected inductance and ca pacitor, which thus saturates theiron core of the reactor so that its inductance falls to a low value.The value of this saturable reactor is somewhat critical, for if itsinductance in the unsaturated state exceeds the critical value, it willnot saturate at the available line voltage and the circuit will notoperate to initiate a discharge in the 'glow relay tube I 3.

This critical value of the saturable reactor is determined by the valueof the series connected capacitor 9 and inductance element I0 as well asby the line voltage. The value of the series inductance and capacitorare so chosen that the sum of their impedance is capacitive which, whenadded to the impedance of the saturable reactorf` reduces the totalimpedance of the circuit to a value which is less than the impedance ofthe saturable reactor alone. Since the current flowing in the circuit isdeterminable by dividing the line voltage by the total impedance of thecircuit, it is only necessary to select the proper values for thecapacitor, inductance element and reactor so that the resultant currentis great enough to saturate the iron core of the reactor man as suchcurrent is limited largely by the resistance of the reactor. N

In the case of an watt fluorescent lamp having a diameter ofapproximately .Lf/g inches and of about 48 inches length, the currentinitially owing in the saturable reactor approximates 0.5 ampere. Thiscurrent flow in the reactor is shown at (A) in Fig. 2 for a completecycle of the alternating current source, and as will be noted is butslightly distorted from a true sinusoidal wave. The wave form of themagnetic flux (B) in the reactor as well as the voltage (C) thereacrossis likewise shown in Fig. 2 where in each instance the ordinaterepresents magnitude and the abscissa time of one cycle of 1.450 of asecond when the 118 volt source is of 60 cycle irequency.

From the voltage wave form of Fig. 2 it will be noted that the peakvoltage across the saturable reactor reaches a value of about 400 volts.voltage is insufficient to initiate a discharge between the electrodes Band 'I of the lamp 5 under any conditions but since this voltage isimpressed across the glow relay tube, a discharge occurs therein. Aspointed out in the above noted Pat- This ent 2,200,443, the resultingglow discharge heats the electrodes; and since at least one electrode isa heat-responsive element, they engage each other and extinguish thedischarge to connect the electrodes 6 and 'I in a series heating circuitto the source which is in parallel to the saturable reactor. Closure ofthe relay contacts occurs in about TLG of a second following theincrease in voltage across the reactor and saturation of its core thusrapidly heating the electrodes of the lamp to an electron-emittingtemperature. When the relay contacts close, the current through thesaturable reactor falls from the momentary value of about 0.5 ampere toa very low value of approximately 15 milliamperes, since the voltagedrop across the reactor is now equal to the voltage drop across the lampelectrodes 6 and 1 which can not exceed 25 volts.

Upon cooling of the electrodes of the glow relay I3, they open, causinga high transient voltage from the inductance element I0 which thusinitiates a discharge between the lamp electrodes 6 and 1. During thecontinuance of the discharge, the lamp voltage is insumcient to saturatethe iron core of the reactor, with the result that such reactorcontinues to draw a small current of only about 50 milliamperes with apower loss of but approximately 1A; watt.

A further advantageous feature of the present circuit, which is notfound in resonant type circuits, is that should the contacts of the glowrelay tube fail to close for any reason, the various circuit elementswill not burn out since, as before noted, the current through thesaturable reactor is but 0.5 ampere, while normal lamp current may be1.4 amperes, which thus gives a wide factor of safety due to thecharacteristics of the saturable reactor.

In Fig. 3 a two-lamp unit is shown which differs from Fig. 1 in theaddition to the circuit of a lamp 22 having a lagging power factor. Thecircuit for the leading lamp 5 is identical to that as shown in Fig. 1.The lagging lamp 22 has one terminal of its electrode 24 connected by aconductor 25 to the conductor I2 and hence to one end of the winding ofa high leakage react ance auto-transformer 23, and in a similar mannerone terminal of the electrode 26 is connected by a conductor 21 to theother end of the winding of the auto-transformer 23, which thusimpresses a voltage of approximately volts across the electrodes of lamp22 and across a glow relay tube 23 identical to the relay tube I3.

When the switch (not shown) is closed as previously mentioned, the lamp5 is energized and a discharge is initiated as above described. At thesame time the full voltage of the autotransformer 23 is impressed acrossthe electrodes of glow relay tube 28, which thus causes operation of therelay tube 28 in the identical manner as above described relative to thelamp 5. Upon opening of the electrodes of the glow relay tube 28 aftercooling, a high transient voltage or "inductive voltage kick isimpressed across the electrodes 24 and 26 from the portion of the high ileakage reactance auto-transformer which is in series with the lamp andthe source of supply, thus initiating a discharge in the lamp 22. Sincethe lamp voltage is below that necessary to cause a discharge in theglow relay tube 23, the latter does not operate so long as the lamp 22continues to operate.

It is to be noted that no saturable reactor is necessary in order tostart the lamp 22 having a lagging power factor because there is a widerange between the higher line voltage and the lamp voltage, whichpresents no problems so far as the utilization of a glow relay tube isconcerned. However, in the case of the leading lamp 5, the lamp voltageis very close to line voltage, and a glow relay tube cannot be utilizedwithout limiting the characteristics of the circuit, such as by asaturable reactor in parallel with the lamp, as herein described. Also,by employing a leading and lagging lamp in a two-lamp unit wherein thelamp currents are approximately 90 apart, not only does such unit morenearly approach unity power factor, but the stroboscopic effect of thelamps is also reduced to a minimum. It thus becomes obvious to thoseskilled in the art that a starting and operating circuit for gaseousdischarge lamps is herein provided wherein the characteristics of thecircuit are such that a glow relay tube can be readily employed with alamp having a leading power factor and despite the fact that the lampvoltage is -very close to line voltage. Moreover, by combining suchleading power factor with a lamp having a lagging power factor, a unitis produced wherein the starting and operating elements arestandard forboth lamps, andthe stroboscopic effect is reduced to a minimum.

Although one specific embodiment of the present invention has beenherein shown .and described, it is to be understood that othermodifications thereof may be made without departing from the spirit andscope of the appended claims.

I claim: l

1. The combination charge lamp provided with electrodes adapted to beheated to an electron emitting temperature, a readily ionizable mediumtherein, ,-a source of electrical energy for heating the said electrodesand for energizing said lamp, an inductance and capacitor interposedbetween said source and one of said electrodes to cause the energizingcircuit for said lamp to have aleading power factor, 'a glow relay tubeoperable to' connect the electrodes of sai'd lamp in a heating circuitwith said source and to thereafter interrupt said heating circuit andcause an -attendant voltage surge from said inductance for initiating adischarge in said lamp, and a saturable reactor in electrical. parallelrelation with said lamp for supplying a potential insufficient toinitiate a discharge in sald n lamp but suficientto cause a discharge insaid glow relay tube and operation thereof.

2. The combination of apair of electrical discharge devices providedwith electrodes therein adapted to be heated to an electron emittingtemperature, a source of electrical energy for heating the saidelectrodes of each lamp 'and for energizing the same, connectionsbetween the electrodes of one of said lamps and said source of' supplyincluding an inductance and acapacitor to cause 'the energizing -circuitfor said lamp to have a leading power factor, a glow relay tube operableto connect the electrodes of said one of said lamps in aheating circuitwith said source and to thereafter interrupt said heating circuit andcause an attendant voltage surge from said inductance for initiating adischarge in said one of said lamps,

a saturable reactor in electrical parallel relation of a gaseouselectric -disrelay tube operable at the voltage supplied by saidauto-transformer to connect the electrodes of the other of said lamps ina heating circuit with said source and to thereafter interrupt saidheating circuit and cause an attendant voltage surge from the inductanceof said auto-transformer for inu itiating and sustaining a discharge inthe other of said lamps whereby the stroboscopic effectof said pair oflamps is reduced to a minimum.

3. The combination of a gaseous electric dis'- charge lamp provided withelectrodes adapted to be heated to an electron emitting temperature, a

readily ionizable medium therein, a source of electrical energy forheating said electrodes and having a voltage; closely approximating thatof the operating voltage of said lamp and of insufficient magnitude toinitiate a discharge between said electrodes,l an inductance andcapacitor interposed between said source and one of said electrodes tocause the energizing circuit for said lamp to have a leading powerfactor, a glow relay tube having a break-down voltage above thatsupplied by said source and operable to connect the electrodes of saidAlamp in a heating circuit vwith said source and to thereafter interruptsaid heating circuit and cause a high transient voltage from saidinductance of lsu-iiicient magnitude to initiate a discharge in saidlamp, and a saturable reactor connected to the energizing circuit forsaid lamp for supplying a voltage insufficient to initiate a dischargein said lamp but of sufficient v magnitude to cause a discharge in saidglow relay tube and attendant operation thereof.

4. The combination of a gaseous electric .dis-

" charge lamp provided with electrodes adapted to be heated to anelectron emitting temperature, a readily ionizable medium thereinasource of electrical energy of the customary domestic potential A forheating said electrodes and having a voltage closely approximating thatof the operating voltage of said lamp and of insuflicient magnitude to4initiate a discharge between said electrodes, an

inductance and capacitor interposed between said source and one of saidelectrodes to cause the energizing circuit for said'lamp to have aleadingv lpower factor, a glow relay tube having a breakdown voltageabove that supplied by said domestic source and operable to connect theelectrodes lo'f said lamp in a heating circuit with said source and tothereafterv interrupt said heating circuit and cause an attendantvoltage surge from said inductance of a magnitudesuiliciently above thevoltage of said source to initiate a discharge in vsaid lamp, asaturable reactor in electrical Parallel relation with said lamp forsupplying a-voltage insufficient to initiate a discharge in said lampbut sufficient lto c'ause la discharge in said glow relay tube andattendant operation thereof, and said reactor remaining in anunsaturated condition and consuming, a very small current duringcontinued operationof said lamp.

,5, The combination of a pair of electrical vdischarge lamps providedwith electrodes thereinY v adapted to be heated to an`electron emittingtemperature and having an -cperating voltage approximating that of adomestic source of supply, la source of electrical energy of thecustomary domestic potential for heating the said electrodes with saidlamp for supplying a non-sinusoidalhighly peaked potential sucient tocause a discharge in said glow relay tube and operation' of each lampandfor energizing the same, `corinections between the electrodesof one ofsaid .lamps and said source of supply including an inductance and acapacitor to cause the energizing circuit for said lamp to have aleading power factor and to permit operation of said lamp at the voltageof said domestic source of' supply, a i I above that supplied by saiddomestic source and operable to connect the electrodes of said lamphaving a leading power factor in a heating circuit with said source andto thereafter interrupt said heating circuit and cause an attendantvoltage surge from said inductance for initiating a discharge in saidlamp having a leading power factor, a saturable reactor in electricalparallel relation with said lamp having a leading power factor forsupplying a voltage of suicent magnitude to cause a discharge in saidglow relay tube and attendant operation thereof, a high leakagereactance auto-transformer connected to said domestic source of supplyand to the other of said lamps to form an energizing circuit having aglow relay tube having a break-down voltage lagging power factor and tosupply a voltage sumciently above that of said domestic source tooperate said lamp having a lagging power factor, and a second glow relaytube having a breakdown voltage above that of said domestic source lauto-transformer for initiating and sustaining a discharge in the lamphaving a lagging power factor whereby the stroboscopic effect of saidpair of lamps is reduced tofa minimum.

, ROBERT F. HAYS. JR.

